Page:The Harveian oration 1890.djvu/30

26 side diminished, the distension of the veins dis- appeared, and the blanched lungs again assumed a rosy hue. Distrusting his own personal observa- tion Dr. Brunton got two observers who knew nothing about the experiment and repeated it before them, noting down their observations, which agreed exactly with his own. It is all but impossible, I think, either to doubt the accuracy of the record of this experiment, or to attribute the phenomena observed, especially the simultaneous distension of the pulmonary artery and the blanching of the lungs, to any other cause than the action of vaso- motor nerves.

Subsequent observers seem to have failed to obtain the striking effects witnessed by Dr. Lauder Brunton, but his account is substantially confirmed by Mr. Bokenham, who tells me that in his experiments* muscarine in a small dose caused rapid fall in the carotid pressure, with, in most cases, a rise in the pulmonary pressure. This rise, however, was of short duration, and the pressure in the pulmonary artery soon fell to normal, whilst that in the carotid more slowly rose to its original level. A large dose produced paralysis of the heart and rapid fall of pressure in both circuits. (Plate I.)

Amyl nitrite (Plate II), given by injection into the jugular vein, or by inhalation, caused a rapid fall of carotid pressure, with simultaneous marked rise of pulmonary pressure. The absolute pressure in the

adopted being that used by Dr. J. Rose Bradford, and described by him in ' Jouni. Physiol.,' vol. x, p. 153.
 * These were performed on cats, dogs, and rabbits, the method